vue 网络图片转Base64

      // 一定要设置为let，不然图片不显示
      let image = new Image();
      // 解决跨域问题
      image.setAttribute('crossOrigin', 'anonymous');
      let imageUrl = '图片地址'
      image.src = imageUrl
      let that = this;
      let dataURL = ''
      // image.onload为异步加载
      image.onload = () => {
        var canvas = document.createElement('canvas');
        canvas.width = image.width;
        canvas.height = image.height;
        var context = canvas.getContext('2d');
        context.drawImage(image, 0, 0, image.width, image.height);
        var quality = 0.8;
        // 这里的dataurl就是base64类型
        dataURL = canvas.toDataURL('image/jpeg', quality); // 使用toDataUrl将图片转换成jpeg的格式,不要把图片压缩成png，因为压缩成png后base64的字符串可能比不转换前的长！
        console.log(dataURL);
       }